1. Field of the Invention
The present invention relates to a method for manufacturing an LCD, and more particularly to a method for manufacturing an LCD capable of improving the efficiency of protrusions of a reflection electrode in a pixel and simplifying the processes.
2. Description of the Prior Art
As is generally known in the art, LCDs may be classified into transmission-type LCDs and reflection-type LCDs according to the kind of light source. The transmission-type LCDs direct artificial light from the back light (or rear light source) fastened to the rear surface of the liquid crystal panel to the liquid crystal and adjust the amount of light depending on the arrangement of the liquid crystal to display color. The transmission-type LCDs using an artificial rear light source, however, consume too much power.
The reflection-type LCDs largely depend on external natural light or artificial light source and have less power consumption than the transmission-type LCDs. However, the reflection-type LCDs have a problem in that external light cannot be used in a dark place or in bad weather conditions.
Both reflection-type and semi-transmission-type LCDs have a reflection material film formed on the lower substrate thereof. A reflection-type LCD and a method for manufacturing the same will now be described mainly with regard to formation of a reflection material film.
FIG. 1 is a sectional view showing a conventional reflection-type LCD.
A conventional reflection-type LCD, as shown in FIG. 1, includes an upper substrate 13 having a color filter layer (not shown) and a common electrode 17 formed thereon, a lower substrate 11 having a thin film transistor (not shown) and a reflection electrode 16 formed thereon, and a liquid crystal 19 interposed between the upper and lower substrates 13 and 11.
The liquid crystal 19 is an optical anisotropic medium arranged in a predetermined direction by an electric field to control the flow of light. Instead of the liquid crystal 19, any medium having optical anisotropic characteristics functioning in a similar manner may be used.
The upper and lower substrates 13 and 11 have a number of optical media arranged on the outer surface thereof to artificially control the polarity condition of light. Particularly, the upper substrate 13 has a scattering film 21, a phase difference plate 23, and a polarization plate 25 successively laminated thereon. The scattering film 21 is a device for scattering light and providing the observer with wider viewing angle. The phase difference plate 23 includes a first phase difference film having the characteristics of λ/4 plate, which affects light propagating through the reflection electrode, and a second phase difference film having the characteristics of λ/2 plate, which is bonded to the first phase difference film. When no voltage is applied (i.e., in an off state), the phase difference plate 23 reverses the phase of propagating light and endows it with phase difference so that a larger amount of light is directed to the exterior and a liquid crystal having higher luminance characteristics is realized. The polarization plate 25 transmits light vibrating in the direction of the transmission axis and absorbs the remaining component.
A conventional method for manufacturing an LCD will now be described with reference to the accompanying drawings.
FIG. 2 is a top view showing a conventional LCD provided with a reflection electrode having protrusions formed thereon and FIGS. 3a to 3e are sectional views showing respective processes taken along line I-II of FIG. 2.
As shown in FIGS. 2 and 3e, the lower substrate 11 has a thin film transistor T formed on a predetermined part of the upper portion thereof in a conventional technology and a protective film 36 formed on a part thereof where the thin film transistor T is formed. The protective film 36 has a plurality of protrusions 37a of resin material formed thereon with a predetermined spacing. The protrusions 37a are distributed on the whole surface on which the thin film transistor T is formed with a predetermined spacing to improve the reflection angle of light.
The protective film 36 having protrusions 37a formed thereon has a reflection electrode 16 formed thereon while being electrically connected to a drain electrode 31 of the thin film transistor. The reflection electrode 16 has protrusions formed thereon by means of the protrusions 37a formed on the underlying protective film 36 so that, when external light is reflected and directed to the exterior again, light incident on the protrusions 37a at various angles are collimated and directed towards a predetermined angle.
An organic insulation film 38 is formed on the front surface of the lower substrate 11 including the protrusions 37a, and a reflection electrode 16 is formed on the organic insulation film 38.
A method for manufacturing the LCD will now be described with reference to FIGS. 3a and 3e. 
As shown in FIG. 3a, a protective film 36 is formed on the front surface of the lower substrate 11 provided with a thin film transistor. A resin film 37 is then formed thereon. In FIG. 3a, reference numeral 27 refers to a gate electrode, 28 is a gate insulation film, 29 is a source electrode, 31 is a drain electrode, and 30 is a semiconductor layer.
As shown in FIG. 3b, exposure and development processes are performed to pattern the resin film and form a plurality of resin film patterns 37b with a predetermined spacing. Alternatively, underlying posts are formed and a resin film is over-coated to form the resin film patterns 37a. 
As shown in FIG. 3c, the resin film patterns are subject to a reflow process by means of heat treatment to form protrusions 37a in a semispherical shape.
As shown in FIG. 3d, an organic insulation film 38 is formed on the front surface of the lower substrate 11 including the semispherical protrusions 37a. The protective film and the organic insulation film are then patterned to form a contact hole 35 so that a predetermined part of the surface of the drain electrode 31 of the thin film transistor is exposed.
As shown in FIG. 3e, a conductive opaque metal film (not shown) having excellent reflection characteristics is deposited on the front surface of the lower substrate 11 including the contact hole 35 and is patterned to form a reflection electrode 16 as a pixel electrode in the pixel region while being connected to the drain electrode 31. The reflection electrode 16 has a corrugated shape by means of the plurality of protrusions 37a. 
Although desired angular distribution of protrusions may be obtained when a resin is used to form protrusions as in the prior art, it is very difficult to reduce the diameter of protrusions to 10 μm or less. Since an interval must be maintained between the protrusions having a diameter of at least 10 μm, utilization of the space inside the pixel cannot be maximized. In addition, additional photo process and heat treatment process must be performed when a resin is used. This makes the processes complicated and increases the manufacturing cost.